1. Field of the Invention
The present invention relates to a polarizing lens that is suitable for use as an eyeglass lens functioning to absorb or transmit light of a specific direction of polarization for the purpose of blocking light such as reflected light having a specific direction of polarization outdoors or the like.
2. Discussion of the Background
Polarizing lenses have been developed to reduce light reflecting off the surface of water, the glare from illumination, and the like so as to improve the field of view in outdoor activities and the like. Polarizing films prepared by stretching a conventional polymer film in a prescribed direction to specify directions of the polarization axes have generally been employed in such polarizing lenses as well as the polarizing elements used in liquid-crystal displays and the like. In this regard, polarizing layers formed by laminating dichroic dyes on orienting films positioned on the surface of a substrate have been developed in recent years. For example, a polarizing element having a polarizing layer and a protective layer on the surface of a transparent substrate as well as having an inorganic intermediate layer of silica (SiO2) or the like as an orienting film between the polarizing layer and the transparent substrate has been proposed as a structure for such polarizing elements employing dichroic dyes. Such polarizing elements are proposed in WO2006/081006, which is expressly incorporated herein by reference in its entirety. By providing a pattern of peaks and valleys in the form of stripes, for example, on an orienting film, the polarizing element is formed so that the polarization axes run either in the direction of the stripes or perpendicular to them.
A polarizing lens for eyeglasses in which the surface of the lens is, for example, divided into middle, left, and right portions, and polarizing films of different directions of polarization axes are incorporated into the divided regions has been proposed in US2008/0252846A1 and Family member U.S. Pat. No. 7,597,442, which are expressly incorporated herein by reference in their entirety. In the eyeglass lens described in US2008/0252846A1, as shown in the plan view of FIG. 9, for example, the optical surface of lens 100 is divided into three parts by dividing lines running vertically (perpendicular) to the line of sight. Among these three divided regions, in center region 101, the polarization axes are straight lines running left and right (horizontally) with respect to the line of sight. In left and right peripheral portions 102a and 102b, that is, in the peripheral portions of the nose side and the ear side, the polarization axes are straight lines running up and down (vertically).
Regions comprised of polarization axes vertically running in different directions are provided in the polarizing lens described in US2008/0252846A1, in contrast to a conventional polarizing lens, in which the polarization axes (absorption axes) are straight lines running horizontally to suppress light reflecting off horizontal surfaces such as the surface of a body of water such as the sea or a river. This is to adapt to the general conditions of glare in an urban environment by taking into account the effects on the horizontal portions of the field of view of reflections off of window glass and the like on the vertical walls of buildings in the urban environment. It is also to adapt to vehicles present to the right and left of the wearer, and to the field of view of vehicle drivers.
However, in the polarizing lens described in US2008/0252846A1, when the polarization axis is sharply distributed perpendicular to a specified direction as shown in FIG. 9, and the orientation of the face is slightly changed, there are cases where the function of blocking reflected light may suddenly decrease. In such cases, they eyes end up being stimulated in an unpleasant manner.
In reality, the direction of polarization of light reflecting off of vertical surfaces such as window glass is not necessary a constant direction. There are many situations where the reflected light cannot be adequately suppressed even when using the polarizing lens disclosed in US2008/0252846A1. The change in the direction of polarization of such reflected light will be described with reference to FIGS. 10 to 13.
FIG. 10 is a diagram showing the direction of polarization of light reflecting off of a horizontal surface such as the surface of a body of water. FIG. 10 is a lateral view of how a ray of incident light Li reflects off horizontal surface 50 in the form of the surface of a body of water, the glossy surface of a table, or the like. The normal line to the position of incidence on horizontal surface 50 is indicated by dotted line v and the reflected light is indicated by arrow Lr. Natural light such as sunlight does not have a definite direction of polarization, but is polarized in every direction. The component of light in which the electric vector oscillates along a plane (the incidence plane) running in the direction of incidence and the direction of reflection, as indicated by arrow p, is called p component (p polarized light), and the component of light in which the electric vector oscillates perpendicular to the incidence plane, as indicated by arrow s, is called the s component (s polarized light). The reflectance of the light changes with the angle of incidence, but in most regions from an angle of incidence of 0° to 90°, the reflectance of p polarized light is lower than the reflectance of s polarized light. At a given angle of incidence (Brewster angle θB), it is known to become zero.
Additionally, the larger the angle of incidence of s polarized light becomes, the greater the reflectance tends to be. In most regions, the reflectance of s polarized light is greater than that of p polarized light. That is, in reflected light Lr, s polarized light is dominant over most of the range of angles of incidence. Accordingly, it is possible to efficiently control light reflecting off the surface of such an object by blocking s polarized light with a polarizer. In particular, since only s polarized light is reflected in light reflecting at the Brewster angle, the reflected light can be suppressed to near zero.
As shown in FIG. 10, when human eye 60 is looking in a horizontal direction, the direction of polarization of the reflected light is transverse relative to eye 60, that is, horizontal. When the polarization axis that blocks the polarization direction (s polarized light) of such reflected light (the direction in which s polarized light is absorbed and p polarized light is passed) is made the absorption axis and a polarizing lens is worn, if the absorption axis is the horizontal direction, light reflecting of a horizontal surface can be suppressed well. When viewing a horizontal surface such as the surface of a body of water, it is sufficient to block s polarized light regardless of the angle of incidence, that is, any polarizing lens having an absorption axis that is horizontal will do, regardless of the position of the sun.
However, light reflecting off of approximately vertical surfaces, such as the exteriors of buildings, the lateral surfaces of vehicles, and window glass has a different direction of polarization. FIG. 11 is a drawing showing the direction of polarization when incident light Li enters from a horizontal direction relative to vertical surface 51. In FIG. 11, portions corresponding to FIG. 10 are denoted by identical numbers and their repeat description is omitted. Reflected light Lr from vertical surface 51 is similarly dominated by s polarized light that is vertical to the surface of incidence, but s polarized light when the light comes from a horizontal direction is in a vertical direction as viewed by human eye 60. That is, to block the light arriving in a horizontal direction that has reflected off a vertical surface relative to human eye 60, it is desirable to wear a polarizing lens with absorption axes lying in the vertical direction.
However, the direction of polarization of reflected light only becomes vertical under special conditions at dawn and dusk, and the direction of polarization of reflected light changes over time. For example, as shown in FIG. 12, the direction of polarization of light Lr reflecting off of vertical surface 51 when incident light Li arrives at a diagonal angle becomes diagonal relative to eye 60 when vertical surface 51 is viewed from below at an angle looking upward. As shown in FIG. 13, at around noon, the light enters vertical surface 51 from a direction vertically above, so the direction of polarization of reflected light Lr becomes nearly horizontal with respect to human eye 60 when looking upward from below. In FIGS. 12 and 13, portions corresponding to FIG. 11 are denoted by identical numbers and their repeat description is omitted.
That is, the direction of polarization of light reflecting off of vertical surface 51 gradually changes over time within a range running from the horizontal to the vertical direction. Additionally, there are also cases where light reflects off of curved surfaces and inclined surfaces on vehicles and the like in addition to buildings. Thus, in the urban environment, there are directions of polarization in directions inclined at various angles. Accordingly, simply making the absorption axes horizontal in the middle and vertical on the left and right sides in the manner described in US2008/0252846A1 ends up causing the effect of reflected light suppression to go unutilized during many periods of the day, resulting in a polarizing lens that cannot function satisfactorily.
Based on the same principle, even revolution of the human eyeball can conceivably change the direction of polarization of reflected light. The angle of incidence of reflected light does not depend just on the displacement of sunlight. For example, when buildings are located close together in the urban environment, multiple reflections between building and building, building and car, and the like can cause the angle of incidence to change to one that differs from the orientation of sunlight. In such cases, when the eyeballs are revolved, causing reflected light arriving from a diagonal direction to enter the eyes, the blocking function of a polarizing lens configured as shown in FIG. 9 is inadequate. That is, so long as the absorption axes of the polarizing lens is linear and the directions are limited to the horizontal and vertical, the suppressive effect on reflected light will be limited and there will be numerous conditions and periods of day when the effect will be inadequate.
In configurations in which the boundary line of the polarization axis (absorption axis) of a lens changes 90° at a boundary, directional revolution of the eyeball will sharply change how well a polarizing lens blocks light; it is undesirable for the eye. Blocking reflected light in diagonal directions when the directions of the absorption axes are divided into individual zones and are discontinuous requires, for example, changing the area of regions in which the polarization axes are vertical in peripheral portions, or assembling polarizing elements with absorption axes aligned in different directions. That is, when the surface of a lens is simply divided up into multiple sections and regions with different absorption axes are provided, multiple variations must be prepared to block polarized light that enters from the diagonal direction and varies or changes the angle of incidence of the light. This is extremely impractical because it requires the wearer to change polarizing lenses based on need. Thus, there is a need for a polarizing lens that does not require the switching out of polarizing lenses and that is capable of flexibly handling directions of polarization of reflected light that change with the angle of incidence of light and directional revolution of the eyeball.